Should I use additional empty category in some categorical problems?
In short: yes, you must allow &quot;do nothing&quot; decision as a first level result.
Your system must decide the action to be taken, including &quot;do nothing&quot; action. This is different to low network outputs, that can be translated as &quot;don't know what to do&quot;.
In other words, the network can result in:

&quot;I don't know what to do now&quot; when all results in the output have low probabilities. (Obviously, this is a bad network result, to be fixed as much as possible).
&quot;I know I must do nothing&quot;, when &quot;do nothing&quot; action has high probability, greater than the others.
&quot;I know I must do W&quot;, when &quot;W&quot; action has high probability, greater than the others.
...

Kind regards.